1. Field of the Invention
The present invention generally relates to interlock switches, and particularly relates to a safety lock for interlock switches.
2. Background Information
A common type of safety interlock includes a switch and an actuator. In a common configuration, the actuator includes a finger and the switch includes a slotted head configured to receive the actuator finger. In one arrangement, positive engagement of the actuator finger in the head slot turns the switch on, while disengagement of the actuator finger from the head slot turns the switch off. While it is common for the actuator to have a single finger, the switch head may have more than one slot. For example, there may be one or more switch actuator openings (e.g., slots) on adjacent or opposing faces of the head, allowing the switch to be mounted in different orientations.
For machine guarding applications, the actuator may be mounted to a moveable guard (or access panel, door, gate, etc.), with the switch mounted in a corresponding fixed position such that closure of the guard causes the actuator to engage the switch. While this arrangement provides reliable machine lockout on guard opening, it does not necessarily prevent accidental or mistaken operation of the switch while the movable guard is open.
Safety locks eliminate, or at least greatly reduce, the possibility of accidental reengagement of the safety interlock. In a common safety lock configuration, the safety lock includes a tab that inserts into the switch head slot that would otherwise be engaged by the actuator finger. Such safety locks usually include a moveable piece (e.g., sliding or rotating) that locks the tab into the slot. The moveable piece is then locked into position using a padlock, for example.
Some implementations of the above type of safety lock do not engage with the head slot as securely as merited by the safety-critical nature of the application. For example, some safety locks, even when locked into place, can be disengaged from the switch head by twisting, pulling, or other manipulation.